Heat exchangers

ABSTRACT

A high-flame facing area heat exchanger in which the air passageways pass both around and through the combustion chamber in a repetitive crisscross pattern. Some of the passageways which pass through the chamber are isolated and connected to feed the burner with preheated combustion air.

United States Patent Richard N. Weatherston St. Paul, Minn.

Feb. 5, 1970 Aug. 24, 1971 Weather-Rite Manufacturing Ramsey County, Minn.

Inventor App]. No. Filed Patented Assignee HEAT EXCHANGERS 10 Claims, 4 Drawing Fig.

U.S.C1. .1 126/110 R, 126/104 A, 126/116 R Int. C1. F2411 3/08 Field oiSmr-ch 126/110, 11OB,116,116B,104,104 A, 90, 91

ZZ I [56] Referencts Cited UNITED STATES PATENTS 1,389,408 8/1921 Wilputte 126/104 A 3,068,854 12/1962 Freeman 126/1 10 Primary Examiner-Charles .1. Myhre Attorney-Robert M. Dunning ABSTRACT: A high-flame facing area heat exchanger in which the air passageways pass both around and through the combustion chamber in a repetitive crisscross pattern. Some of the passageways which pass through the chamber are isolated and connected to feed the burner with preheated combustion air.

PATENTEU M824 lsm SHEET 1 OF 2 INVENTOR RICH/a RD N. WEATHERSTON ELMO 1:

ATTORNEY HEAT EXCHANGERS BACKGROUND OF THE INVENTION In the prior art, heat exchangers typically burn gas and air in a combustion chamber and direct the hot exhaust gases through an extended metal tube which can be folded upon itself, coiled, or arranged in a variety of configurations. The air which is to be heated is circulated amongst this tube configuration to pick up heat by conduction. Such an arrangement generates a large amount of heat near the combustion area and a low amount of heat far down the tube from the combustion area. As a result, the systems have been found to be inefficient, Furthermore, tubes near the combustion area receive relatively excessive amounts of heat and often burn out. The size of the prior art units are cumbersome and the known arrangements do not lend themselves to multiple zone heating applications. My invention avoids the above mentioned problems by means of a unique, compact heat exchanger configuration.

SUMMARY OF THE INVENTION Briefly, the present invention contemplates an elongated combustion chamber which has a narrow portion along one of the long sides. Over substantially the entire length of this narrow portion air and gas apertures supply and generate a flame which heats the chamber. The air to be heated is circulated not only around the combustion chamber but also through a large number of crisscrossing tubes which pass through the combustion chamber.

Maximum efficiency in a heat exchanger is accomplished by subjecting all of the metal heat transfer surfaces to both hot exhaust gases and direct thermal radiation from the flame. My invention, in contrast to the prior art, provides a design wherein a very large percentage of the available heat exchanging surface faces the flame and thereby enjoys this ideal situation. In addition, the various heat exchange surfaces across the width and length of the present heat exchange unit receive the same degree of heating so that the design has no unduly hot or cold spots as in the prior art. Thus, the present invention is particularly well suited to zone heating applications as will be described presently. It is apparent from the foregoing that it is an object of my invention to provide an improved heat exchanger design. It is a further object to provide a heat exchanger of high efficiency wherein localized hot and cold spots are minimized and the flame facing heat transfer surface area is maximized. Further objects and advantages will become apparent from the following description and drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic sectional end view of the major components and passageways of the preferred embodiment showing generally the direction of air flow through the apparatus by means of arrows.

FIG. 2 is an enlarged schematic sectional cutaway drawing showing in greater detail the burner elements of FIG. 1.

FIG. 3 is a schematic sectional side view of the apparatus of FIG. 1 showing some additional elements including a typical zone heating modification.

FIG. 4 is a perspective detailed view of the burner assembly showing the slide out capability utilized in the preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I a furnace housing is shown having a separate compartment 12 in which an air blower I4 is positioned. A brief reference to FIG. 3 will demonstrate that the preferred embodiment utilizes, in fact, a pair of blowers 14 and 16 driven by a common shaft 18 from a motor 20 operating through a belt and pulley connection. Referring simultaneously to the end view of FIG. I and the side view of FIG. 3 it may be seen that air from blowers l4 and 16 is directed into a plenum chamber 22. Disposed within plenum chamber 22 is a combustion chamber 24 within which gas and air are burned. It should be understood that the present invention has applicability for different types of fuel and is not limited to the particular type of heat generating mechanism shown herein. In the preferred embodiment gas enters by means of a fuel feed tube 26 and is directed therefrom through a series of small nozzles into combustion chamber 24 along substantially the entire length of the combustion chamber 24. The direction along which fuel feed tube 26 is positioned is defined as the elongate direction for convenience although it should be understood that some versions of my invention could indeed be shorter in the elongate direction than in the direction orthogonal to the elongate direction. Air is introduced into a pair of plenum chambers 28 and 30 which are in communication with the combustion chamber by means of a series of perforated plate members 32 and 34.

Air from blowers l4 and 16 enters plenum chamber 22 and passes around combustion chamber 24, as indicated by the arrows, into an exhaust plenum chamber 40 and thence outward through a vent 42 to be utilized as desired. In addition, air from the blowers passes through a large number of crisscrossing interwoven heat exchange tubes 44 and 45 which are positioned to pass through combustion chamber 24 diagonally. In the preferred embodiment sixteen diagonal tubes 44 and l6diagonal tubes 46 are shown although any number may be utilized depending on the particular size heat exchanger contemplated. A further understanding of the crisscrossing arrangement of the heat exchanging tubes 44 and 46 may be had by reference to FIG. 3 wherein two of these tubes are shown by means of dashed lines 44 and 46. To keep the drawing simple the remaining tubes are not shown with dashed lines in FIG. 3.

As mentioned earlier, maximum efficiency in a heat exchanger is accomplished when the heat exchanging surfaces contact not only the hot combustion gases but also view or face the combustion area so that heat may be received by direct thermal radiation. Since, in my invention, the combustion takes place in the area between perforated plates 32 and 34 it may be readily seen in FIG. 1 and FIG. 2 that a maximum amount of the interior surface of tubes 44 and 46 faces the combustion area. Also, the whole combustion chamber receives approximately equal heating so that there are no localized hot or cold spots. Furthermore, the combustion area extends from top to bottom in FIG. 3 so that all of the tubes 44 and 46 and all of the combustion chamber receives an equal amount of conductive and radiant-heating. Consequently, the heat exchanger of the present invention is particularly suitable for zone heating application as indicated in FIG. 3.

In FIG. 3 a separate compartment 50, not shown in FIGS. 1 and 2, has been shown in the exhaust plenum chamber 40 defined by walls 52 and 54. With this type of separate compartment, heat from just a few selected tubes may be directed to a particular zone. The amount of flow is controlled by a suitable damper or butterfly valve 56. Any number or size of compartments such as enclosure 50 may be positioned to accept heat from various different sets of tubes in FIG. 3 without difliculty since the entire exchanger is heated equally along its length. Therefore, zone heating applications become relatively easy with the present invention.

In order to provide air to the combustion feed plenum chambers 28 and 30 some of the diagonal heat exchange tubes 44 and 46 are closed off from the normal air flow path and connected so that the air from those tubes is directed into plenum chambers 28 and 30. This operation may be more readily understood with reference to FIG. 2.

In FIG. 2, two of the diagonal tubes have been connected so as to direct preheated air into the combustion chamber. The section of FIG. 2 passes through the center of diagonal tube 44A. The air from tube 44A passes into a chamber 60 which is closed off from the normal exhaust plenum chamber 40 shown in FIG. 1. The air continues from chamber 60 through a vent hole 62 and against a perforated deflector plate 64. Deflector plate 64 serves to prevent a localized blast of air against perforated plate 34 and helps distribute the incoming air throughout plenumchamber 30. Small perforations in perforated plate 64 ensure that the air will not be totally blocked from the particular area of perforated plate 34 opposite plate 64. The preheated air in plenum chamber 30 passes through perforated plate 34 into the combustion area inside combustion chamber 24. In FIG. 2 the very next cross diagonal tube 46A is utilized to bring preheated air to the other side of the combustion chamber. Since tube 46A is lower, in FIG. 2, than tube 44A, it is not shown in section but enters a compartment 66 in the same manner. The preheated air from tube 46A passes through compartment 66, through a suitable opening, and against a deflector plate 68 in plenum chamber 28. The air passes through perforated member 32 as described with respect to the other side of the heat exchange unit. After combustion takes place the hot exhaust gas passes over the diagonal heat exchange tubes and travels down to the opposite end of combustion chamber 24 to an area generally designated by the numeral 70 in FlG. 1. From there the exhaust gases travel out an exhaust pipe 72 which is shown more clearly in FIG. 3.

FIG. 4 shows in a much shortened version how the design of the burner mechanism permits easy removal. Perforated members 32 and 34 and the gas supply pipe 26 are supported by an end plate 80 and a pair of lengthwise support members 82 and 84. Consequently, the whole assembly may be slid easily in and out of a generally rectangular recessed portion 25 at the side of combustion chamber 24. When the burner assembly is inserted in recessed portion 25 it serves to define and segregate the two combustion plenum chambers 28 and 30.

It will be readily apparent that numerous variations may be made to the present invention without departing the spirit and scope of the concept herein involved. For example, an additional blower may be connected to supply air exclusively to the diagonal tubes which are connected to feed plenum chambers 28 and 30. The passageways can be modified in shape or a bypassageway employed to mix cool air with the heated air. Thus, I do not intend to be limited to straight diagonal tubes, or to a combustion chamber formed exactly in the shape of chamber 24, nor to the particular heat generating means utilized, or any of the passageway configurations shown except as defined by the appended claims.

I claim:

1. A fuel burning heat exchanger comprising in combination:

a combustion chamber having an elongate direction and a multitude of apertures along a first side which is generally parallel to said elongate direction, said multitude of apertures adapted to admit air to said combustion chamber over substantially the entire elongate length of the combustion chamber and further having a plurality of apertures contiguous to the air admission apertures, said plurality of apertures connected to a source of fuel and adapted to admit fuel to said combustion chamber over substantially the entire length of the combustion chamber;

first plenum chamber means connected to said multitude of apertures so as to supply air thereto;

a plurality of air passageways disposed around and through said combustion chamber shaped to present a maximum area toward the combustion area inside said combustion chamber; means connecting at least one of said air passageways disposed through the combustion chamber to said first plenum chamber means so as to supply preheated air thereto; and blower means connected to said plurality of air passageways operable to move air therethrough. 2. The apparatus of claim 1 in which said plurality of air passageways disposed around said combustion chamber are defined by an outer housing surrounding said combustion chamber, said plurality of passageways around the combustion chamber comprising the spaces between the combustion chamber and said outer housing; and in which the plurality of air passageways disposed through said combustion chamber comprise heat conductive tunnels passing through generally orthogonal to said elongate direction.

3. The apparatus of claim 2 in which said tunnels comprise a first groups of generally similar tubes interwoven with a second group of generally similar tubes.

4. The apparatus of claim 3 in which said first group of tubes pass through the combustion chamber generally in a first diagonal direction and said second group of tubes pass through the combustion chamber generally in a second diagonal direction which forms an angle with respect to said first diagonal direction so that the exit ends of the tubes pass on either side of said first side of said combustion chamber with said multitude of apertures therebetween.

5. The apparatus of claim 4 in which said multitude of apertures comprise first and second apertures members positioned on each side of said plurality of fuel admission apertures and said first plenum chamber means comprises a first chamber in communication with said first apertured member and a second chamber in communication with said second apertured member.

6. The apparatus of claim 5 in which at least one of said first group of generally similar tubes is connected at its exit end to said first chamber and at least one of said second group of generally similar tubes is connected at its exit end to said second chamber.

7. The apparatus of claim 6 including a second plenum chamber means located and connected between said blower means and the entrance ends of said first and second groups of tubes and the entrance ends of the passageways which pass around the combustion chamber.

8. The apparatus of claim 7 in which said second plenum chamber means is defined by said outer housing and comprises the space between said outer housing and the second side of said combustion chamber which second side is opposite from said first side and disposed generally between the entrance ends of said first and second groups of tubes.

9. The apparatus of claim 8 including deflection plates disposed in said first and second chambers positioned to spread and diffuse air introduced from said tubes and in which plurality of fuel admitting apertures comprise a series of nozzles in a fuel feed tube disposed between said apertured plates and generally along said elongate direction.

10. The apparatus of claim 9 in which said apertured plates and said nozzled fuel feed tube comprise a separate assembly adapted to be removably positioned in a recess in said first side of said combustion chamber so as to form therein said first and second chambers. 

1. A fuel burning heat exchanger comprising in combination: a combustion chamber having an elongate direction and a multitude of apertures along a first side which is generally parallel to said elongate direction, said multitude of apertures adapted to admit air to said combustion chamber over substantially the entire elongate length of the combustion chamber and further having a plurality of apertures contiguous to the air admission apertures, said plurality of apertures connected to a source of fuel and adapted to admit fuel to said combustion chamber over substantially the entire length of the combustion chamber; first plenum chamber means connected to said multitude of apertures so as to supply air thereto; a plurality of air passageways disposed around and throUgh said combustion chamber shaped to present a maximum area toward the combustion area inside said combustion chamber; means connecting at least one of said air passageways disposed through the combustion chamber to said first plenum chamber means so as to supply preheated air thereto; and blower means connected to said plurality of air passageways operable to move air therethrough.
 2. The apparatus of claim 1 in which said plurality of air passageways disposed around said combustion chamber are defined by an outer housing surrounding said combustion chamber, said plurality of passageways around the combustion chamber comprising the spaces between the combustion chamber and said outer housing; and in which the plurality of air passageways disposed through said combustion chamber comprise heat conductive tunnels passing through generally orthogonal to said elongate direction.
 3. The apparatus of claim 2 in which said tunnels comprise a first groups of generally similar tubes interwoven with a second group of generally similar tubes.
 4. The apparatus of claim 3 in which said first group of tubes pass through the combustion chamber generally in a first diagonal direction and said second group of tubes pass through the combustion chamber generally in a second diagonal direction which forms an angle with respect to said first diagonal direction so that the exit ends of the tubes pass on either side of said first side of said combustion chamber with said multitude of apertures therebetween.
 5. The apparatus of claim 4 in which said multitude of apertures comprise first and second apertures members positioned on each side of said plurality of fuel admission apertures and said first plenum chamber means comprises a first chamber in communication with said first apertured member and a second chamber in communication with said second apertured member.
 6. The apparatus of claim 5 in which at least one of said first group of generally similar tubes is connected at its exit end to said first chamber and at least one of said second group of generally similar tubes is connected at its exit end to said second chamber.
 7. The apparatus of claim 6 including a second plenum chamber means located and connected between said blower means and the entrance ends of said first and second groups of tubes and the entrance ends of the passageways which pass around the combustion chamber.
 8. The apparatus of claim 7 in which said second plenum chamber means is defined by said outer housing and comprises the space between said outer housing and the second side of said combustion chamber which second side is opposite from said first side and disposed generally between the entrance ends of said first and second groups of tubes.
 9. The apparatus of claim 8 including deflection plates disposed in said first and second chambers positioned to spread and diffuse air introduced from said tubes and in which plurality of fuel admitting apertures comprise a series of nozzles in a fuel feed tube disposed between said apertured plates and generally along said elongate direction.
 10. The apparatus of claim 9 in which said apertured plates and said nozzled fuel feed tube comprise a separate assembly adapted to be removably positioned in a recess in said first side of said combustion chamber so as to form therein said first and second chambers. 